1. Field of the Invention
The present invention relates to the field of wireless communications, and particularly relates to a distance estimation method and device as well as a node localization method and apparatus.
2. Description of the Related Art
Wireless communications is a kind of communications in which electromagnetic waves are utilized instead of cables, and has been widely used so far. According to the different frequencies of the electromagnetic waves, the communications protocols and the application scenarios of a wireless communications network are also different. For example, the wireless communications network may include the Global System for Mobile Communications (GSM), Radio Frequency Identifier (RFID), satellite communications, ultrasonic waves, Ultra Wide Band (UWB), or Bluetooth based network.
In such a wireless communications network, the distance estimation of two nodes plays an very important role in the communications process among respective nodes. For example, it is possible to estimate the distance between two nodes located in a specific environment by using the received signal strength between the two nodes. In theory, the received signal strength is inversely proportional to the distance between the two nodes. That is, the stronger the received signal strength is, the shorter the distance between the two nodes is; and vice versa.
However, there may exist spatial change (or called “environmental change”) in a specific environment due to a movable or immovable obstacle therein. This kind of spatial change is also called “environmental noise” which may result in uncertainty in the distance estimation process between two nodes. For example, the environmental noise may include white noise and burst noise. Especially the burst noise may generate unpredictable influence on the distance estimation process, thereby resulting in a relatively large error in the distance estimation result. In general, the burst noise refers to one which suddenly occurs, whose amplitude is high, and whose time of duration is short. For example, a human being, who enters into and then immediately departs from a specific space in which plural nodes are located, may block the signal transmission being conducted between two nodes therein. This kind of blocking may result in the burst noise which may dramatically affect the received signal strength.
Conventionally the influence of the environmental noise is not taken into account. As such, when the burst noise occurs, the distance estimation process cannot get an accurate distance estimation result.
In order to deal with the burst noise, a solution has been proposed in which it is possible to utilize, before conducting the distance estimation process, a filter to directly remove the burst noise by conducting a filtering process. However, at present, there does not exist a method by which the position of the burst noise can be accurately determined. For this reason, when conducting the filtering process, it is easy to remove a valid signal, and/or it is impossible to completely remove the burst noise. As a result, there still exists a certain level of offset in the obtained distance estimation result.